The present invention relates to a synthesis device for orthopaedia and traumatology.
More particularly, the present invention relates to a device for the synthesis of a bone fracture after its reduction by means of a body which allows to fix the fractured region, keeping it in the correct position for the time required by the bone to strengthen.
Various devices used to perform this operation are known.
Among these, the devices most frequently used are screws of the self-tapping or through type, possibly cooperating with plates which are arranged laterally to the bone in the region where the fracture is present.
All these devices are very troublesome to position and also have problems linked, among other issues, to the compactness of the bone in the fractured region.
More particularly, screws of the self-tapping type rely on a good grip of the thread, but this does not always occur.
Through screws associated with external plates are very bulky and must usually be removed when the bone has consolidated in the fracture region.
Substantially U-shaped brackets are also known which are made of materials having shape memory; their wings are inserted in two holes formed in the bone on opposite sides with respect to the fracture line.
These brackets, when heated, shorten in the intermediate region between the two ends inserted in the bone or the two ends bend toward each other, connecting the fracture.
However, these brackets have the drawback that they act only by traction in the external cortical region of the bone and in many cases do not allow to control the fracture region and keep it in the correct position.
U.S. Pat. No. 5,584,695 discloses an apparatus for anchoring a prosthetic tooth 21 to a patient's jawbone 22 including a root screw 26, with a longitudinal bore 29, for implantation in the jawbone 22, and a temperature-sensitive shape-memory cylindrical coupling pin 34 for fixing a stump 35, with its own longitudinal bore 39 and mounting the prosthetic tooth 21, to the root screw 26. The coupling pin 34 extends into the aligned bores 29 and 39, and at temperatures below its transformation temperature range (TTR) the coupling pin 34 is thinner than the diameters of such bores 29 and 39 for easy insertion and extraction therefrom, while at temperatures above its TTR the coupling pin 34 expands inside the bores 29 and 39 to lock the mounting stump 35 to the root screw 26. In one specific embodiment (FIG. 2C), the cylindrical coupling pin 34 has a forked end portion 47 with two or more prongs 48 which open up at temperatures above the TTR for locking the coupling pin 34 into either or both bores 29 and 39.
FR-A-2727304 discloses a self-locking medullary canal bone implant having at least one section made from a metal alloy with a shape memory effect, situated at one or both ends or along its whole length. The implant is shaped for convenient positioning and its shape changes on heating or cooling so that it grips the inside of the bone and holds firmly in place.